Curable adhesive compositions for bonding one or more substrates

Abstract

Compositions that cure upon exposure to actinic radiation are disclosed. In some embodiments, the curable adhesive composition comprises: a) one or more radiation curable oligomers or prepolymers, the radiation curable oligomers or prepolymers having at least one carbon-carbon double bond-containing group at the terminus; b) one or more diluent monomer components containing at least one polymerizable group; c) optionally one or more adhesion promoting additives of organic or inorganic acid acrylic monomers; and optionally, one or more rheology modifiers; one or more plasticizers; and one or more additives. The curable composition can be used in adhesives that structurally bond a variety of substrates, including different substrates. In some embodiments, the cured reaction product of the composition has a wide use temperature range from-20 DEG C to 120 DEG C. The curing reaction product of this embodiment exhibits a cohesive failure of greater than 50% over the temperature range. The cured composition will maintain adhesive strength at temperatures above its Tg.

Description

Technical Field

[0001] The present disclosure generally relates to compositions that cure upon exposure to actinic radiation, such as ultraviolet (UV) radiation. Background Art

[0002] Curable adhesive compositions find widespread use in bonding, particularly in the transportation and electronics industries. These industries bond many different substrates to form transportation parts (e.g., aircraft, automotive, marine, railroad, and truck parts) and electronic devices (e.g., computers, mobile phones, tablet computers). Of course, transportation parts and electronic devices will include subcomponents used in those parts and devices.

[0003] One of the greatest difficulties in all adhesive applications is the bonding of substrates with different coefficients of thermal expansion (CTE). Common examples include the bonding of aluminum to glass, glass to plastic, ceramic to plastic, and rubber to metal. In addition, the stress caused by extreme temperatures and thermal cycling during use sometimes complicates difficult situations.

[0004] This localized movement of material, or thermal stress, is concentrated at the adhesive layer between the adhesive and the substrate. It is important that the adhesive maintains adequate bond strength while being flexible enough to withstand these movements associated with thermal cycling.

[0005] Bonding dissimilar substrates requires adhesives that bond to a variety of surface chemistries and, after curing, can withstand the stresses associated with different coefficients of thermal expansion. To help minimize stresses from thermally induced strains, it is desirable that the adhesive be flexible while maintaining sufficient toughness to achieve structural durability. In practice, the flexibility of the adhesive can be controlled by the selection and concentration of prepolymers / oligomers, monomers, plasticizers, and filler loading.

[0006] Acrylic curable adhesive compositions contain various additives to help control the properties in both the uncured and cured states.

[0007] Because plasticizer is easy to regulate the processability of uncured adhesive and adjust the ability of the physical property of cured adhesive, it is a common ingredient in many adhesive compositions.For cured adhesive composition, the effect of plasticizer is to embed itself between polymer chains, thereby increase segment mobility and produce dilution effect in polymer matrix.By reducing the rotational energy barrier in polymer matrix, the cured composition of gained benefits from improved flexibility.Elastic modulus, glass transition temperature, tensile strength and hardness are all reduced, but elongation at break increases.Although plasticizer increases the flexibility and softness of adhesive, this flexibility is not always permanent.Plasticizer often migrates out from material, thereby causes material embrittlement.In order to attempt to alleviate plasticizer loss, the structure and molecular weight of plasticizer can be selected accordingly.

[0008] Diluent monomers of various chemical structures and properties are commercially available, and they can be used to adjust the overall properties (bulk properties) and bonding properties of the composition. For example, using a monomer with low Tg and / or low modulus will increase flexibility, while using a monomer with high Tg will increase the rigidity or modulus of the curable adhesive composition. Depending on the addition level or combination of the diluent monomer, the expected effect can be controlled. Although these properties can be effectively controlled, there is also a compromise. For example, as the concentration of the toughening monomer increases, other properties (such as high temperature toughness and bond strength) decline. For this reason, it may be difficult to use a monomer to balance the properties of the adhesive for bonding different substrates.

[0009] It remains a challenge to produce flexible adhesive compositions that maintain high bond strength over a wide temperature range to bond dissimilar substrates. Disclosed herein is an unexpected method by which the flexibility and bond strength of curable compositions are increased over a large temperature range without the need for the extensive use of plasticizers or other softening monomers. Summary of the invention

[0010] One embodiment of the present disclosure provides a curable adhesive composition comprising: a) one or more radiation-curable oligomers or prepolymers having at least one group containing a carbon-carbon double bond at the end; b) one or more diluent monomer components containing at least one polymerizable group; c) optionally one or more adhesion-promoting additives of organic or inorganic acid acrylic monomers; d) optionally one or more rheology modifiers; e) optionally one or more plasticizers; and f) optionally one or more additives (such as pigments, dyes, fillers, stabilizers, UV absorbers, antioxidants, processing oils, etc.).

[0011] One embodiment of the present disclosure provides a curable adhesive composition having a wide use temperature range of -20°C to 120°C. The cured reaction product of this embodiment will exhibit greater than 50% cohesive failure within this temperature range. The cured composition will maintain adhesive strength at temperatures above its Tg.

[0012] One embodiment of the present disclosure provides a curable adhesive composition for structurally bonding dissimilar substrates, such as metal and plastic, particularly low surface energy aluminum and polycarbonate.

[0013] One embodiment of the present disclosure provides a curable adhesive composition having extremely high flexibility, wherein the tensile modulus at 23°C is less than 100 and the elongation at break is greater than 200% (ASTM D412). DETAILED DESCRIPTION

[0014] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0015] As used herein, about or "approximately" with respect to a numerical value refers to the numerical value ±10%, preferably ±5%, more preferably ±1% or less.

[0016] As used herein, at least one means one or more (i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9 or more). With respect to ingredients, the notation refers to the type of ingredient, not the absolute number of molecules. Thus, "at least one polymer" means, for example, at least one type of polymer, i.e., one type of polymer or a mixture of several different polymers can be used.

[0017] As used herein, the terms "comprising / comprises / comprised of" are synonymous with "including / includes", "containing / contains", and are inclusive or open-ended and do not exclude additional unrecited members, elements, or method steps.

[0018] When amounts, concentrations, sizes and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits, or preferred upper and lower limits, it should be understood that any range that can be obtained by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0019] Preferred and preferably are often used herein to refer to embodiments of the present disclosure that can provide specific benefits in certain circumstances. However, the recitation of one or more preferred or preferred embodiments does not mean that other embodiments are not useful, and is not intended to exclude those other embodiments from the scope of the present disclosure.

[0020] Unless otherwise specified, the molecular weights given herein refer to the number average molecular weight (Mn). Unless otherwise specified, molecular weight data can be obtained at 35°C according to DIN 55672-1:2007-08 by gel permeation chromatography (GPC) calibrated against polystyrene standards. w For M n The polydispersity index is a measure of the molecular weight distribution in a given polymer sample. The polydispersity index is calculated by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn).

[0021] As used herein, a curable one-component (1K) composition is a single formulation that is commercially stable enough to be prepared, stored, and shipped to an end user. A 1K composition can be used without adding any additional components and will crosslink or cure when exposed to suitable conditions. As used herein, a two-component (2K) composition has two or more components. Each component is prepared, stored, and shipped separately from the other components. The components are mixed immediately before use. The mixing of the components triggers a curing reaction, so commercial storage after mixing is not possible.

[0022] As used herein for each of the various embodiments, the following definitions apply:

[0023] Unless specifically defined otherwise, (meth)acrylate refers to at least one of acrylate and methacrylate. "Vinyl" refers to (CH2=CH-). "(Meth)acryloyl" refers to at least one of acryloyl and methacryloyl, "acryloyl" refers to (CH2=CHCO-), and "methacryloyl" refers to (CH2=C(CH3)CO-).

[0024] Actinic radiation includes electron beam, ultraviolet light, visible light, and combinations thereof. Desirably, the actinic radiation used to cure the composition has a wavelength of about 200nm to about 1000nm. Available ultraviolet light (UV) includes, but is not limited to, UVA (about 320nm to about 410nm), UVB (about 290nm to about 320nm), UVC (about 220nm to about 290nm), and combinations thereof. Available visible light includes, but is not limited to, blue light, green light, and combinations thereof. Such available visible light has a wavelength of about 450nm to about 550nm.

[0025] Unless specifically defined otherwise, "acyl" refers to the general formula -C(O)alkyl.

[0026] Unless specifically defined otherwise, "acyloxy" refers to the general formula -O-acyl.

[0027] Unless specifically defined otherwise, "alcohol" refers to the general formula alkyl-OH.

[0028] Unless specifically defined otherwise, "alkenyl" or "lower alkenyl" refers to a straight, branched or cyclic carbon chain having 1 to about 16 carbon atoms, advantageously about 1 to about 6 carbon atoms, and having at least one double bond between the carbon atoms in the chain. Examples include, for example, ethylene, propadiene, butylene, butadiene, hexene, hexadiene, 5,5-dimethyl-1-hexene and cyclohexene. Unless specifically limited otherwise, alkenyl can be unsubstituted, monosubstituted or polysubstituted, with substituents in any possible position.

[0029] Unless specifically defined otherwise, "alkoxy" refers to the general formula -O-alkyl.

[0030] Unless otherwise specifically defined, "alkyl" refers to a straight chain, branched or cyclic alkyl having 1 to about 9 carbon atoms, including, for example, methyl, ethyl, propyl, butyl, hexyl, octyl, isopropyl, isobutyl, tert-butyl, cyclopropyl, cyclohexyl, cyclooctyl, vinyl and allyl. Unless otherwise specifically defined, alkyl can be saturated or unsaturated and substituted or unsubstituted. Unless otherwise specifically limited, cyclic alkyl includes monocyclic, bicyclic and polycyclic, such as norbornyl, adamantyl and related terpenes.

[0031] Unless specifically defined otherwise, "alkylamino" refers to the general formula -(NH)-alkyl.

[0032] Unless otherwise specifically defined, the "dialkylamino group" refers to the general formula -N-(alkyl) 2. Unless otherwise specifically limited, the dialkylamino group includes cyclic amine compounds such as piperidine and morpholine.

[0033] Unless specifically defined otherwise, "alkylmercapto" refers to the general formula -S-alkyl.

[0034] Unless otherwise specifically defined, "alkynyl" or "lower alkynyl" refers to a straight, branched or cyclic carbon chain having 1 to about 16 carbon atoms, advantageously about 1 to about 6 carbon atoms, and having at least one triple bond between carbon atoms in the chain. Examples include, for example, acetylene, butyne and hexyne. Unless otherwise specifically limited, alkynyl can be unsubstituted, monosubstituted or polysubstituted, with substituents in any possible position.

[0035] Unless specifically defined otherwise, an aromatic ring is an unsaturated ring structure having about 5 to about 6 ring members and including only carbon as ring atoms. Unless specifically defined otherwise, an aromatic ring may be substituted or unsubstituted.

[0036] Unless specifically defined otherwise, "aryl" refers to a substituted or unsubstituted aromatic ring system comprising only carbon as ring atoms, for example phenyl, biphenyl, or naphthyl.

[0037] Unless specifically defined otherwise, "aroyl" refers to the general formula --C(=O)-aryl.

[0038] Unless specifically defined otherwise, a carbocycle is a ring structure having about 3 to about 8 ring members, being substituted or unsubstituted, comprising only carbon as ring atoms, for example, benzene or cyclohexane.

[0039] The terms "halogen," "halo," or "hal," when used alone or as part of another group, mean chlorine, fluorine, bromine, or iodine.

[0040] Unless specifically defined otherwise, a heteroaromatic ring is an unsaturated ring structure having from about 5 to about 8 ring members, being substituted or unsubstituted, having carbon atoms and one or more heteroatoms (including oxygen, nitrogen and / or sulfur) as ring atoms. Heteroaromatic rings (or groups) also include fused polycyclic systems in which one or more monocyclic aromatic rings or monocyclic heteroaromatic rings are fused to another heteroaromatic ring. Examples of heteroaromatic rings (or groups) include, but are not limited to, furan, thiophene, pyrrole, oxazole, thiazole, isoxazole, pyrazole, imidazole, oxadiazole, triazole, tetrazole, pyridine, pyrimidine, pyrazine, purine, benzothiazole, benzimidazole, benzofuran, indole, quinoline, quinoxaline.

[0041] Unless specifically defined otherwise, "heteroaryl" refers to a heteroaromatic ring.

[0042] Unless specifically defined otherwise, heterocycle is a saturated ring structure having about 3 to about 8 ring members, substituted or unsubstituted, with carbon atoms and one or more heteroatoms (including oxygen, nitrogen and / or sulfur) as ring atoms. Examples of heterocycles include, but are not limited to, oxetane, thietane, azetidine, diazetidine, tetrahydrofuran, thiolane, pyrrolidine, dioxolane, oxathiolane, imidazolidine, dioxane, piperidine, morpholine, piperazine, and derivatives thereof. Unless specifically limited otherwise, heterocycles include monocyclic, bicyclic and polycyclic, such as azaadamantyl and tropanyl.

[0043] Unless specifically defined otherwise, the term "phenacyl" refers to the general formula -phenyl-acyl.

[0044] Room temperature refers to a temperature of about 25°C.

[0045] Unless otherwise specifically limited, the term "substituted" means substitution at one or more any possible positions with at least one of the following substituents. Substituents of the above moieties useful in the disclosed compounds are those groups that do not significantly reduce the biological activity of the disclosed compounds. Substituents that do not significantly reduce the biological activity of the disclosed compounds include, for example, H, halogen, N3, NCS, CN, NO2, NX1X2, OX3, C(X4)3, OAc, O-acyl, O-aroyl, NH-acyl, NH-aroyl, NHCOalkyl, CHO, C(halogen)3, COOX4, SO3H, PO3H2, SO2NX1X2, CONXX2, C(O)CF3, alkyl, alcohol, alkoxy, alkylthiol, alkylamino, dialkylamino, sulfonamide, or thioalkoxy, wherein X1 and X2 each independently comprise H or alkyl, or X1 and X2 together form part of a heterocyclic ring having from about 4 to about 7 ring members and optionally one additional heteroatom selected from O, N or S, or X1 and X2 together form part of an imide ring having from about 5 to about 6 members and X4 comprises H, alkyl, lower alkylhydroxy, or alkyl-NX1X2. Unless specifically limited otherwise, if multiply substituted, the substituents may be in one or more of any possible positions.

[0046] The term "aliphatic" means a saturated or unsaturated, straight chain, branched or cyclic hydrocarbon group.

[0047] The term "polymer" means a molecule having a small number of repeating monomer units (e.g., 10-25,000 units) that have been polymerized to form the molecule, and includes oligomers and prepolymers, which are subsets of the term polymer, typically having a smaller number of repeating monomer units and a degree of polymerization.

[0048] As used herein, "one or more" refers to at least one, and includes 1, 2, 3, 4, 5, 6, 7, 8, 9 or more of the mentioned species. Similarly, "at least one" means one or more, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9 or more. "At least one" as used herein with respect to any component refers to the number of chemically different molecules (i.e., the number of different types of the mentioned species), rather than the total number of molecules. For example, "at least one polyol" means that at least one type of molecule within the definition of a polyol is used, and means that there may be two or more different types of polyols within the definition, but does not mean that there must be only one type of said polyol.

[0049] The disclosed compounds include any and all isomers and stereoisomers. Generally, unless otherwise expressly stated, the disclosed materials and methods may alternatively be described as comprising any suitable component, part or step disclosed herein, consisting of any suitable component, part or step disclosed herein, or consisting essentially of any suitable component, part or step disclosed herein. The disclosed materials and methods may additionally or alternatively be described as being free of, or substantially free of, any component, material, ingredient, adjuvant, part, species and step used in prior art compositions or otherwise not necessary for realizing the functions and / or purposes of the present disclosure.

[0050] Unless otherwise indicated, all percentages referred to with respect to the compositions described herein refer to weight percentages (wt %) relative to the final composition having all components.

[0051] In one embodiment, the UV-curable adhesive composition comprises: (meth) acrylic prepolymer; plasticizing adhesion promoting monomer; adhesion promoting diluent monomer; reactive monomer diluent; photoinitiator; optional filler; and optional one or more additives. The UV-curable adhesive composition is preferably a one-component (1K) system rather than a two-component (2K) system.

[0052] (Meth)acrylic prepolymer

[0053] Useful materials for use as (meth)acrylic prepolymers include (meth)acrylic functional siloxanes, polyacrylates, polyurethanes, polyethers, polyolefins, polyesters, copolymers thereof, and combinations thereof. In some embodiments, the (meth)acrylic prepolymer has at least two (meth)acryloyl functional groups, preferably pendant (meth)acryloyl functional groups. Desirably, the pendant (meth)acryloyl groups consist of -OC(O)C(R 1 )=CH2, where R 1 is hydrogen or methyl.

[0054] Preferably, the (meth)acrylic prepolymer is a (meth)acryloyl-terminated polyacrylate prepolymer having the following structure:

[0055]

[0056] Each F part is composed of -OC(O)C(R 1 )=CH2 represented by a (meth)acryloyl side group, wherein R 1 is hydrogen or methyl.

[0057] (Meth) acrylic prepolymers may desirably have a molecular weight (Mn) of less than 100000 g / mol, in some embodiments about 3000 to about 50000 g / mol. Desirably, (meth) acrylic prepolymers have a molecular weight higher than about 16000 g / mol, so as to provide increased elongation and flexibility for the cured reaction product of the adhesive composition. In addition, (meth) acrylic prepolymers may desirably have a viscosity of about 2000 Pas (200000 cPs) to about 8000 Pas (800000 cPs) at 25 ° C (77 ° F), more desirably about 4500 Pas (450000 cPs) to about 5000 Pas (500000 cPs). (Meth) acrylic prepolymers are commercially available from Kaneka Corporation, Japan as trade names RC220C, RC210C, RC200C and RC100C. It is believed that RC220C, RC210C and RC200C are each terpolymers (varying by molecular weight) of a combination of substituted and unsubstituted alkyl acrylates such as ethyl acrylate, 2-methoxyethyl acrylate and n-butyl acrylate, while RC100C is a homopolymer of n-butyl acrylate.

[0058] Plasticizing Adhesion Promoting Monomers

[0059] Plasticized adhesion promoting monomer increases the pliability of the cured reaction product of adhesive composition, and also helps the cured reaction product of adhesive composition to the adhesion of substrate.Plasticized adhesion promoting monomer is also covalently bonded in the polymer network of cured composition.What can be used as plasticized adhesion promoting monomer is acrylic acid, methacrylic acid and combination thereof.At present, the inventor does not know that other materials that can be used as plasticized adhesion promoting monomer in said composition.The use of a large amount of plasticized adhesion promoting monomer is undesirable, because it has harmful effect to cured product modulus and moisture resistance.

[0060] Adhesion promoting diluent monomer

[0061] Adhesion promoting diluent monomers reduce the viscosity of the uncured adhesive composition and also contribute to the adhesion of the cured reaction product of the adhesive composition to the substrate. Plasticized adhesion promoting monomers are also covalently bonded to the polymer network of the cured composition. It has been demonstrated that N,N-dimethylacrylamide can be used as an adhesion promoting diluent monomer. At present, the inventors are not aware of other materials that can be used as adhesion promoting diluent monomers in the composition.

[0062] Reactive Monomer Diluent

[0063] The reactive monomer diluent increases the flexibility of the cured reaction product of the adhesive composition. The reactive monomer diluent also covalently bonds to the polymer network of the cured composition. The reactive monomer diluent will not be (meth)acrylic acid or dimethylacrylamide. Monomers having one or more reactive (meth)acrylate groups can be used as reactive monomer diluents. Preferably, the reactive monomer diluent is a monofunctional (meth)acrylate, as these allow the cured reaction product of the composition to have increased elongation. Useful monofunctional (meth)acrylates can be represented by the general structure CH2=C(R)COOR 2 Contemplated, wherein R is H, CH3, C2H5, or halogen (such as Cl), and R 2 It contains C 1-8 The molecular skeleton of a monocyclic or bicyclic alkyl group, a 3-8 membered heterocyclic group with at most two oxygen atoms in the heterocyclic ring, H, alkyl, hydroxyalkyl, or aminoalkyl, wherein the alkyl part is C 1-20 Straight, branched or cyclic carbon atom chains. Among the specific monofunctional (meth) acrylate monomers, it is particularly desirable and corresponding to some of the above structures are hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, methyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, cyclohexyl (meth) acrylate, 2-aminopropyl (meth) acrylate, isobornyl (meth) acrylate, isodecyl (meth) acrylate and 2-ethylhexyl (meth) acrylate. In addition, β-carboxyethyl acrylate (such as commercially available from Rhodia under the trade name SIPOMER) is usefully used in the practice of the present invention. A combination of two or more of the above monofunctional (meth) acrylates can be used.

[0064] In some embodiments, it is useful for the reactive monomer diluent to have a high glass transition temperature (Tg) of 50°C or greater and / or to be hydrophobic.

[0065] Reactive monomer diluents having a high Tg provide increased strength and improved modulus to the cured reaction product of the curable composition.

[0066] The hydrophobic reactive monomer diluent provides the cured reaction product of the curable composition with improved bond strength durability and moisture resistance in the application environment. An indicator of the hydrophobicity of the reactive monomer diluent is that the ratio of C atoms to O atoms of the molecular skeleton is greater than 3:1, preferably greater than 4:1.

[0067] Relationship between plasticizing adhesion promoting monomer and adhesion promoting diluting monomer

[0068] The plasticizing adhesion promoting monomer is used in a weight ratio of 1 part plasticizing adhesion promoting monomer: 4 parts adhesion promoting diluent monomer to 1 part plasticizing adhesion promoting monomer: 20 parts adhesion promoting diluent monomer. The cured reaction product of the adhesive composition prepared using a plasticizing adhesion promoting monomer: adhesion promoting diluent monomer ratio outside of these ranges may not provide satisfactory substrate bond strength, tensile modulus, and / or bond durability during exposure to a humid environment.

[0069] Relationship between plasticizing adhesion promoting monomers and reactive monomer diluents

[0070] The adhesion promoting diluent monomer is used in a weight ratio of 3 parts adhesion promoting diluent monomer: 2 parts reactive monomer diluent to 1 part adhesion promoting diluent monomer: 2 parts reactive monomer diluent. The cured reaction product of the adhesive composition prepared using an adhesion promoting diluent monomer: reactive monomer diluent ratio outside of these ranges may have reduced substrate bond strength and / or bond durability during exposure to a humid environment.

[0071] Photoinitiator

[0072] When the curable composition is exposed to actinic radiation, the photoinitiator increases the speed of the curing process.Desirably, the photoinitiator is added to the composition in an amount effective to respond to the actinic radiation and initiate and induce curing of the composition.

[0073] Suitable photoinitiators useful for ultraviolet (UV) actinic radiation curing of monoolefin and polyolefin monomers include free radical generating UV initiators such as substituted benzophenones and substituted acetophenones, benzoin and its alkyl esters, and xanthones and substituted xanthones. Photoinitiators include diethoxyacetophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, diethoxyxanthone, chlorothioxanthone, azobisisobutyronitrile, N-methyldiethanolamine-benzophenone, and mixtures thereof. Specific examples of photoinitiators suitable for use herein include, but are not limited to, photoinitiators commercially available from Ciba Specialty Chemicals under the trade names "IRGACURE" and "DAROCUR", specifically IRGACURE 184 (1-hydroxycyclohexyl phenyl ketone), 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one), 369 (2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone), 500 (a combination of 1-hydroxycyclohexyl phenyl ketone and benzophenone), 651 (2,2-dimethoxy-2-phenylacetophenone), 1700 (a combination of bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentyl)phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one), 819 [bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide], 2022 [IRGACURE 819 dissolved in DAROCUR 1173 (described below)], and DAROCUR 1173 (2-hydroxy-2-methyl-1-phenyl-1-propan-1-one) and 4265 (a combination of 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one); and visible light [blue] photoinitiator dl-camphorquinone and IRGACURE784DC. Of course, combinations of these materials can also be used herein. Other photoinitiators that can be used herein include alkyl pyruvates (such as methyl pyruvate, ethyl pyruvate, propyl pyruvate and butyl pyruvate), and aryl pyruvates (such as phenyl pyruvate, benzyl pyruvate), and appropriately substituted derivatives thereof.Photoinitiators particularly suitable for use herein include: UV photoinitiators such as 2,2-dimethoxy-2-phenylacetophenone (e.g., IRGACURE 651), and 2-hydroxy-2-methyl-1-phenyl-1-propanone (e.g., DAROCUR 1173), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g., IRGACURE 819 and IRGACURE 2022); and a UV / visible light photoinitiator combination of bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentyl)phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one (e.g., IRGACURE 1700); and the visible light photoinitiator bis(5-2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium (e.g., IRGACURE 784DC).

[0074] In some applications, LED devices are used to generate UV radiation to cure the composition. LED devices have advantages over old mercury vapor technology (such as cooler operating temperatures and lower energy use). However, LED devices typically emit UV radiation at 395nm and higher. In some applications, these high UV radiation wavelengths may result in undesirable lower cure rates and cure levels in the composition when used with conventional photoinitiators. It has been demonstrated that Type II photosensitizers (such as Esacure 1001M, Esacure ONE, ITX) can be used to cure compositions exposed to LED-generated radiation and are preferred for this application.

[0075] additive

[0076] The composition may optionally include one or more additives. Additives that may be used in the composition may include fillers; adhesion promoters, such as organofunctional siloxane adhesion promoters, such as 3-aminopropyltrimethoxysilane and / or 3-methacryloxypropyltrimethoxysilane; thixotropic agents and rheological modifiers, such as hydrogenated castor oil, fatty acid amides, or expandable plastics (such as PVC); non-reactive diluents; non-reactive plasticizers, such as phthalates, reactive and non-reactive thermoplastic polymers, including acrylic polymers, functional (e.g., containing reactive moieties such as -OH and / or COOH) acrylic polymers, non-functional acrylic polymers, acrylic polymers; acrylate block copolymers, acrylic polymers with tertiary alkylamide functionality, polysiloxane polymers, polystyrene copolymers, divinylbenzene copolymers, polyetheramides, polyvinyl acetal, polyvinyl butyral, polyvinyl chloride, methylene polyvinyl ether, cellulose acetate, styrene acrylonitrile, amorphous polyolefins, olefin block copolymers [OBC], polyolefin plastomers, thermoplastic polyurethanes, polyacrylonitrile, ethylene acrylate copolymers, ethylene acrylate terpolymers, ethylene butadiene copolymers and / or block copolymers, and styrene butadiene blocks, such as Elvacite resins available from Mitsubishi Chemical America; antioxidants, such as hindered amines and / or hindered phenols; alkoxysilane moisture scavengers, such as vinyl trimethoxy silane; colorants and fluorescent dyes.

[0077] The additive filler may include, for example, inorganic fillers such as chalk, powdered limestone, precipitated silica and / or pyrogenic silica, zeolite, bentonite, carbonates (such as calcium carbonate and magnesium carbonate), sulfates (such as barium sulfate), diatomaceous earth, aluminum oxide, clay, titanium oxide, iron oxide, zinc oxide, sand, quartz, flint, mica, powdered glass, metal powder, other ground minerals, silane-treated silica, (meth)acrylate-treated silica; organic materials such as carbon black, graphite, wood fiber, wood powder, sawdust, cellulose, cotton, pulp, wood chips, chopped straw, husks, ground walnut shells and other chopped organic fibers; short fibers such as glass fibers, glass fibers, polyacrylonitrile, carbon fibers, Kevlar fibers or polyethylene fibers; hollow spheres with a mineral shell or a plastic shell, such as Glass or Materials. Combinations of the above fillers may also be useful.

[0078] In some embodiments, the curable composition has the following components and ranges: Ranges are in weight % based on the weight of the composition.

[0079] (Meth)acrylic prepolymer 10-90％ 20-75％ 20-55 Adhesion promoting diluent monomer 1.0-50％ 8-35％ 12-25 Reactive Monomer Diluent 0-50％ 4-35 5-25 Plasticizing Adhesion Promoting Monomers 0.01-20％ 0.01-10％ 0.1-5 Photoinitiator 0.1-5％ 0.2-3％ 0.5-1 filler 0-40％ 0-30％ 5-15 additive 0-40％ 0-30％ 1-20

[0080] In some embodiments, using less than 10 wt % of the adhesion-promoting diluent monomer based on the weight of the curable composition provides lower bond strength to some plastic substrates. In some embodiments, using more than 25 wt % of the adhesion-promoting diluent monomer based on the weight of the curable composition increases the tendency of the curable composition to absorb moisture.

[0081] The use of some plasticized adhesion promoting monomers in curable compositions provides a higher modulus and increased moisture resistance for the cured reaction product of the composition. However, the use of plasticized adhesion promoting monomers exceeding about 5 wt % by weight of the curable composition provides little or no benefit while increasing costs. In some embodiments, the curable composition comprises 5 wt % or less, preferably 2 wt % or less of the plasticized adhesion promoting monomer by weight of the composition.

[0082] The components are uniformly mixed into a curable composition. Typically, mixing starts with prepolymers and monomers, followed by the addition of additives, fillers and photoinitiators and mixing. The mixed composition should be packaged to isolate actinic radiation, thereby avoiding premature curing initiation. The uncured composition can have a viscosity of 1 to 100 Pas. In some embodiments where the curable composition is extruded during application, a viscosity of about 5 to 50 Pas is more preferred. Of course, the viscosity can be adjusted to be suitable for application methods and applications.

[0083] In use, the curable composition is arranged on the surface of the first substrate, and the second substrate is placed on the first substrate so that the surface is in contact with the provided adhesive. One of the substrates is at least partially transparent to actinic radiation. Actinic radiation passing through the radiation transparent substrate is provided to initiate the curing reaction in the curable composition. Preferably, the cured composition will be in an irreversible solid form with a substantially non-sticky feel. Preferably, the cured composition is not a pressure-sensitive adhesive. Once the composition is cured, it will bond the first substrate to the second substrate. Typical substrates include any combination of ceramics, glass, polymers and metals. The combination of different monomers makes the curable composition particularly useful for bonding a polymer substrate to a non-polymer substrate (such as a metal).

[0084] In some embodiments, the monomer combination and monomer ratio and the plasticizing effect of the prepolymer enable the cured reaction product of the curable adhesive composition to maintain bond strength and flexibility over a wide temperature range (-20° C. to 120° C.). This makes the curable composition suitable for bonding substrate combinations with different expansion rates (such as polymers and metals).

[0085] In some embodiments, the monomer combination and monomer ratio and prepolymer enable the cured reaction product to maintain flexibility and bond strength under a range of humidity conditions. This makes the curable composition suitable for bonding substrates that will be exposed to high temperatures and high relative humidity during use. Preferably, the cured composition can maintain at least 60% of the normal cured strength after being exposed to 85° C. and 85% relative humidity for one week (7 days).

[0086] The following examples are included for illustrative purposes so that the present disclosure may be more easily understood, and are in no way intended to limit the scope of the present disclosure unless otherwise specifically provided.

[0087] The foregoing description is intended to be illustrative, and it should be understood that variations and modifications may be employed without departing from the spirit and objectives of the present invention as defined in the following claims.

[0088] Viscosity is measured at 25°C using a parallel plate rheometer or a cone and plate rheometer (such as Anton Paar MCR 302) using a 50 mm diameter cone or a 25 mm diameter parallel plate.

[0089] The samples were prepared by spreading an adhesive with 1 mm glass spacer beads on one substrate surface and placing a second substrate surface on the spread adhesive to provide two substrates with a 1 mm thick adhesive layer between them. The placed adhesive was cured by exposure to UV light. After the samples were cured, they were tested.

[0090] Ultraviolet (UV) curing was performed using an array of UV-LEDs (375 nm or 405 nm) (each with approximately 700 mW / cm 2 or greater UV radiation energy).

[0091] After curing, some of the cured reaction products were kept in a chamber maintained at 85°C and 85% RH for 7 days (1 week). After this exposure, the samples were further tested.

[0092] The peel strength was measured using a modified version of ASTM D1876. A transparent plastic substrate was bonded to a metal substrate using a 1 mm adhesive layer between the substrates. The adhesive was cured by exposure to an LED source through the plastic substrate for 60 seconds. The source had a power of 700 mW / cm 2The plastic substrate was bonded to the metal plate using a structural MMA adhesive (such as Loctite AAH3500) after curing. Once the adhesive is cured, the metal plate and metal substrate are placed in a tensile tester and pulled at a rate of 50 mm / min. The peel strength is measured and the failure mode is also visually inspected by estimating the total bonding area of ​​the adhesive remaining on the bonding surface of the plastic substrate and the metal substrate. The failure mode is reported as % cohesive failure.

[0093] The tensile strength at break, elongation at break and tensile modulus were evaluated according to ASTM D412.

[0094] The glass transition temperature (Tg) is evaluated using ASTM E1640-04 and is the peak value of tan delta measured using a TA Instruments DMA Q800. Although a cured composition may have multiple Tg peaks, the associated Tg will be the Tg of the overall cured composition. This is labeled Tg2. Some plasticizing adhesion promoters will reduce Tg2 when added to the composition. This is called the Tg2 depression effect.

[0095] Example 1: Prophetic compositions

[0096] The adhesive composition can be prepared from a mixture of the following materials: (meth) acrylic prepolymer (300-600 g); adhesion promoting diluent monomer (100-250 g); reactive monomer diluent (100-250 g); plasticizing adhesion promoting monomer (1-50 g); optional toughening filler (20-150 g); photoinitiator (2-10 g). In some embodiments, one or more optional additives can be added to the above composition, for example: preservatives; antioxidants, such as hindered phenols (0.5-5 g) or hindered amines (1-50 g); colorants or pigments or fluorescent dyes (0.01-1 g); and non-bonding plasticizers, such as phthalates (1-100 g).

[0097] The prophetic mixture will be a 1K system that can be used to bond different substrates (such as polymers and metals). In one use, the mixture can be placed between and in contact with the bonding surfaces of adjacent substrates and cured to bond those substrates. The prophetic example 1 material can be cured by exposure to actinic radiation (such as UV light, preferably UV radiation from an LED source with a wavelength of about 390nm or greater). It is expected that the cured reaction product of the prophetic example 1 material has a flexible structure, wherein the plasticizing effect of the high Tg reactive monomer diluent helps to maintain toughness at high temperatures while allowing cohesive failure at low temperatures.

[0098] Example 2: Prepolymer Type and Effect on Physical Properties

[0099] Curable compositions were prepared using various prepolymer types with and without plasticizing adhesion promoting monomers. All amounts are in % by weight based on the weight of the composition. To compare the plasticizing effect, the following properties were measured: modulus at 23°C, modulus at 120°C, and glass transition temperature (Tg). The compositions and data are shown in the table below.

[0100]

[0101] 1N,N-Dimethylacrylamide

[0102] 2-Isobornyl Acrylate

[0103] 3. Acrylic

[0104] 4Silane-treated fumed silica

[0105] 5. Antioxidants, colorants

[0106] 6Omnirad 819

[0107]

[0108] 1N,N-Dimethylacrylamide

[0109] 2-Isobornyl Acrylate

[0110] 3. Acrylic

[0111] 4Silane-treated fumed silica

[0112] 5. Antioxidants, colorants

[0113] 6Omnirad 819

[0114] Example 2 shows the effectiveness of using acrylic acid in the above composition to reduce the modulus and Tg of the reaction product of the composition. Six different prepolymers were used to compare the effects of not containing acrylic acid (a series) and containing acrylic acid (b series). Overall, the effectiveness was better when using a polymer system with a molecular weight of 16kDa (Mn) or greater.

[0115] Sample 1: When aliphatic polyurethane was used as the prepolymer, the acrylic monomer reduced the 23°C modulus, however, the Tg increased as expected.

[0116] Sample 2: Telechelic polybutadiene with a MW of 4450 Da did not show any softening effect.

[0117] Sample 3: Telechelic polyacrylate with MW 13600 did not show any softening effect.

[0118] Sample 4: Telechelic polyacrylate with MW 16700 did not show any softening effect.

[0119] Sample 5: Telechelic polyacrylate with a MW of 25200 shows an unexpected and surprising softening effect when acrylic acid is added to the composition. The material softens at temperatures below Tg and hardens at temperatures above Tg.

[0120] Sample 6: Telechelic polyacrylate with a MW of 32600 shows an unexpected and surprising softening effect when acrylic acid is added to the composition. The material softens at temperatures below Tg and hardens at temperatures above Tg.

[0121] Example 3: Plasticization of (meth)acrylic prepolymers by different materials

[0122] Use identical (meth) acrylic prepolymer and plasticized adhesion promoting monomer and different candidate plasticizing materials, prepare curable composition.Example 3 compares the plasticizing effect of various materials mixed in UV curable adhesive system (it comprises 3-33kDa (meth) acrylic prepolymer).Test Tg, modulus and stripping behavior, to evaluate plasticizing effect.All amounts shown below are all in g.

[0123]

[0124] 1RC 310C 33 kDa, available from Kaneka

[0125] 2N,N-Dimethylacrylamide

[0126] 3-Isobornyl acrylate

[0127] 4 Fumed Silica

[0128] 5. Antioxidants

[0129] 6Omnirad 819

[0130] 7 Acrylic

[0131] 8-2-Carboxyethyl Acrylate (β-CEA)

[0132] 9 2-Hydroxyethyl Methacrylate Monophosphate and Diphosphate

[0133] 9Tritolyl Phosphate (TCP)

[0134] 10-Ethylhexyl acrylate

[0135] Sample 7 is a composition with no plasticizer added to establish a baseline.

[0136] Sample 8 is a baseline composition that also includes acrylic acid as a plasticizing adhesion promoting monomer. The results for Sample 8 show that acrylic acid suppresses the Tg of the cured composition compared to Sample 7, wherein the cured reaction product is softer at temperatures below the Tg and harder at temperatures above the Tg.

[0137] Sample 9 is a baseline composition that also includes 2-carboxyethyl acrylate (β-CEA) as a possible plasticizing adhesion promoting monomer. β-CEA is a carboxylic acid-containing monomer with a homopolymer Tg of approximately 15.4°C (measured by DSC). β-CEA also reduces the cured reaction product Tg, which is expected for a monomer with a Tg lower than the baseline composition. What is unexpected about Sample 9 is the effective effect that β-CEA reduces the Tg more significantly than expected for an alternative low Tg monomer (see Sample 11) at the same load.

[0138] Sample 10 is a baseline composition that also includes tricresyl phosphate (a known plasticizer). The cured reaction product of the composition of Sample 10 exhibits no change in Tg and little change in modulus.

[0139] Sample 11 is a baseline composition that also includes isooctyl acrylate. Isooctyl acrylate was selected because it has a low homopolymer Tg of -54°C and is used in the art as a substitute for plasticizers to lower the Tg of adhesive compositions, e.g., it behaves as a plasticizing monomer due to its low Tg. The cured reaction product of the composition of Sample 11 has the smallest change in Tg compared to the control, indicating that isooctyl acrylate does not exhibit the unique and effective Tg suppression effect observed for acrylic acid or β-CEA in Samples 8 and 9.

[0140] By applying between the metal substrate and the UV transparent plastic substrate, irradiated with 405nm LED at 0.8W / cm 2 The compositions prepared in Example 3 were tested for T-peel adhesion strength with 1 mm of adhesive cured for 60 seconds. The following metal substrates were tested: Steel, single-sided polished, grade RS-14, from Q-Lab ("Steel"); bare aluminum 2024T3, grade AR-14, from Q-Lab ("Aluminum"); bright tin plated CRS, minimum 0.002" plating, from ACT Test Panels LLC ("Bright Tin Plated CRS"); and copper sheet C110, from Online Metals ("Copper"). The UV transparent plastic substrate used for bonding to the metal substrates was Sabic Lexan LS2-111 polycarbonate (from Standard Plaque Inc.). Ambient (23°C) T-peel adhesion strength data for the compositions in Example 3 are reported below. All values ​​are reported in N / mm. The results are also shown in Figure 1 middle.

[0141]

[0142] At 23°C, Samples 8 and 9, which contain a plasticizing adhesion promoting monomer, show the highest bond strengths. Sample 7, which contains no plasticizing component, shows similar bond strengths to steel and aluminum, but shows reduced bond strengths to bright tin plated CRS and copper. Samples 10 and 11 show that the addition of other types of reactive or non-reactive plasticizers causes an overall loss of bond strength at this test temperature.

[0143] In addition to ambient temperature (23°C) performance, the adhesive must also be able to be used over a wide temperature range depending on exposure to the target application. T-peel adhesion tests were performed at -20°C and 120°C to demonstrate the superior performance of the composition comprising a plasticizing adhesion promoting monomer.

[0144]

[0145] Results are shown in Figure 2 middle.

[0146] When tested at -20°C, the plasticizing adhesion promoting monomers in Samples 8 and 9 provided more than twice the bond strength provided by the benchmark and other plasticizing additives.

[0147] To further emphasize the importance of the unexpected plasticizing properties of (meth) acrylic acid and β-CEA, the adhesion via the T peel test was compared with sample 12, which includes a reference composition also containing 2-hydroxyethyl methacrylate ester of phosphoric acid (HEMA phosphate). This is a common adhesion promoter in the art that does not impart the unexpected Tg reduction characteristics of (meth) acrylic acid or β-CEA. The total modulus of the cured composition is lower than the benchmark, but the Tg is higher than the benchmark. All amounts shown below are in g.

[0148]

[0149] 11 2-Hydroxyethyl Methacrylate Phosphate (HEMA Phosphate)

[0150] The T-peel adhesion of Sample 12 at -20°C was compared to Samples 8 and 9 and the results are shown in the table below.

[0151]

[0152] The results are also shown in Figure 3 middle.

[0153] At -20°C, Sample 12 was brittle and showed no peel adhesion strength to steel or aluminum. Adhesion to tinned CRS and copper was reduced compared to Samples 8 and 9. Therefore, the unexpected reduction in Tg observed in Samples 8 and 9 is a property that affects low temperature peel adhesion strength.

[0154] At 120°C, the modulus of all compositions was approximately equal except for Sample 8. Sample 8, which contained acrylic monomers, produced a particularly unexpected property of higher base modulus at elevated temperatures, resulting in excellent bond strength. Sample 9 performed as expected at this temperature.

[0155]

[0156] Results are shown in Figure 4 middle.

[0157] In addition to the broad temperature performance, the cured composition in Sample 8 also maintained bond strength after exposure to 85°C and 85% relative humidity (RH) for 7 days compared to the baseline composition and similar compositions without the (meth)acrylic acid.

[0158]

[0159] The results are also shown in Figure 5 middle.

[0160] Example 3 demonstrates that acrylic acid used as a plasticizing adhesion promoting monomer in a curable composition has a unique and unexpected ability to promote flexibility in the cured reaction product and maintain the bond strength of the cured composition over a wide temperature range. This was unexpected because the Tg of acrylic acid is approximately 106° C. Furthermore, it was unexpected that acrylic acid was able to impart these advantages even after the cured composition had been exposed to long-term high temperature and high humidity exposure.

[0161] Example 4: Ratio of Adhesion Promoting Diluent Monomer to Reactive Monomer Diluent

[0162] Curable compositions were prepared from the same (meth)acrylic prepolymer and acrylic acid as the plasticizing adhesion promoting monomer, keeping the total monomer concentration constant while varying the ratio of the adhesion promoting diluent monomer to the reactive monomer diluent.

[0163] Cured T-peel bond specimens were prepared and tested with and without exposure to 85°C / 85% relative humidity for 7 days. The specimens for Example 4 were prepared using the same substrates from Example 3. All quantities shown below are in grams.

[0164]

[0165] Bond strength values ​​are reported in N / mm relative to the metal substrate.

[0166]

[0167] The results are also shown in Figure 6 (T-peel strength on steel), Figure 7 (T-peel strength on aluminum), Figure 8 (T-peel strength on bright tin plated CRS) and Fig. 9 (T-peel strength on copper).

[0168] For the metal substrates tested, the optimal ratio of adhesion promoting diluent monomer to reactive monomer diluent is 1: 1 to 2: 1, preferably 3: 2. When the adhesion promoting diluent monomer concentration exceeds this ratio, the cured reaction product shows lower peel strength after being exposed to 85°C and 85% relative humidity for 1 week.

Claims

1. A radiation-curable adhesive composition, comprising: 10 to 99 wt% of a (meth)acrylic prepolymer; 1 wt % to 50 wt % of an adhesion promoting diluent monomer; 0.01 wt % to 20 wt % of a plasticizing adhesion promoting monomer; 0 to 50 wt % of a reactive monomer diluent; photoinitiator; and optionally one or more additives; The wt % are based on the weight of the adhesive composition and total 100.

2. The composition of claim 1, wherein the plasticizing adhesion promoting monomer is used in a weight ratio of 1 part plasticizing adhesion promoting monomer: 4 parts adhesion promoting diluent monomer to 1 part plasticizing adhesion promoting monomer: 20 parts adhesion promoting diluent monomer.

3. The composition of claim 1 or claim 2, wherein the adhesion promoting diluent monomer is used in a weight ratio of 3 parts adhesion promoting diluent monomer: 2 parts reactive monomer diluent to 1 part adhesion promoting diluent monomer: 2 parts reactive monomer diluent.

4. The composition of any one of claims 1-3, wherein the adhesion promoting diluent monomer is N,N-dimethylacrylamide.

5. The composition of any one of claims 1 to 4, wherein the plasticizing adhesion promoting monomer is (meth)acrylic acid.

6. The composition of any one of claims 1 to 5, wherein the monofunctional reactive monomer diluent is isobornyl acrylate.

7. The composition of any one of claims 1 to 6, comprising: 20 to 50 wt% of a (meth)acrylic prepolymer; 15 to 30 wt % of N,N-dimethylacrylamide as the adhesion-promoting diluent monomer; 0.1 to 5 wt % of (meth)acrylic acid as the plasticizing adhesion promoting monomer; and 5 to 25 wt% of a monofunctional reactive monomer diluent.

8. The composition of any one of claims 1 to 7, comprising at least 0.1 wt. % of additives.

9. The cured reaction product of the radiation curable adhesive composition of any one of claims 1 to 8.

10. An article comprising a radiation-curable adhesive composition disposed between a first substrate and a second substrate, wherein the adhesive composition comprises: 10 to 99 wt% of a (meth)acrylic prepolymer; 1 wt % to 50 wt % of an adhesion promoting diluent monomer; 0.01 wt % to 20 wt % of a plasticizing adhesion promoting monomer; 0 to 50 wt % of a monofunctional reactive monomer diluent; as well as Photoinitiator; The wt % are based on the weight of the adhesive composition and total 100.

11. The article of claim 10, wherein the plasticizing adhesion promoting monomer is used in a weight ratio of 1 part plasticizing adhesion promoting monomer: 4 parts adhesion promoting diluent monomer to 1 part plasticizing adhesion promoting monomer: 20 parts adhesion promoting diluent monomer.

12. The article of claim 10 or 11, wherein the adhesion promoting diluent monomer is used in a weight ratio of 3 parts adhesion promoting diluent monomer: 2 parts reactive monomer diluent to 1 part adhesion promoting diluent monomer: 2 parts reactive monomer diluent.

13. The article of any one of claims 10-12, wherein the adhesion promoting diluent monomer is N,N-dimethylacrylamide.

14. The article of any one of claims 10-13, wherein the plasticizing adhesion promoting monomer is (meth)acrylic acid.

15. The article of any one of claims 10-14, wherein the first substrate is a polymer and the second substrate is a metal.

16. The article of any one of claims 10-15, wherein the radiation curable adhesive composition comprises at least one additive.

17. The article of any one of claims 10-16, wherein one of the first substrate or the second substrate is transparent to actinic radiation.

18. The article of any one of claims 10 to 17, which is a transportation component or an electronic device.

19. Use of a radiation-curable adhesive composition for bonding transportation parts or electronic devices, wherein the composition comprises: 10 to 99 wt% of a (meth)acrylic prepolymer; 1 wt % to 50 wt % of an adhesion promoting diluent monomer; 0.01 wt % to 20 wt % of a plasticizing adhesion promoting monomer; 0 to 50 wt % of a reactive monomer diluent; photoinitiator; and optionally one or more additives; The wt % are based on the weight of the adhesive composition and total 100.

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